Variable-constriction nozzle



Dec. 7, 1954 Q JR I 2,696,110

VARIABLE-CONSTRICTION NOZZLE Filed May 2, 1952 I INVENTOR. ALFRED Jeaamgm.

BY jl f romvn's turbulence.

United States Patent '0 256965110 v VARIABLE-CONS'IRICTION. NozzrnAlfred J". Eggers, Jr.,' LosAlt0s,

I Application May2, 1952 S'erial No.. 285,782.

' 4 ch. 13-141 (Granted-under. Title 35,1 S..Code}(,1952),1sec. 266)This: invention relates. to nozzles adapted for developing: highsupersonic" speeds: with; particular-application to use in wind tunnelswhere the characteristics of bodies subjected to airflow are to bedetermined.

In winrhtunneli use. flexibility and adaptability to various speedrequirements. is often-of. highest; importance. Not only is it desirablethat air speed changes be readily made, but it.ise;aIso important thatthesechanges be made easily andiquicklyand with maintenance ofi'economyof operation.

In methods heretoforev in use modification oftunnel air flow has beenobtained by usecof fixed or variable geometry nozzles including aneffuser located upstream from: the.- nozzle test section in which thehighest supersonic air. speeds are secured: and'a diffuser locateddownstream of the test section. In the case of fixed; geometry nozzlesit becomes necessary to replace one nozzle by another of differentdesign, a procedure which is time consuming and aerodynamicallyinefficient due to the excessively high power required to start andoperate the tunnel. In the case of variable geometry nozzles of prioruse the operator is hindered by the complexity of the adjustingmechanism. 7

The objects of this invention therefore include the provision of nozzleconstruction which is simple in form, which is easily manipulated tomodify air flow speed, and which operates efficiently to establish andmaintain the required high supersonic air speeds.

Other objects and features of the invention will become apparent onconsideration of the following description of an embodiment of theinvention taken with the accompanying drawings, in which Fig. 1 is aschematic flow diagram of the nozzle and related equipment;

Fig. 2 is a diagrammatic showing of the movable nozzle sections andadjusting mechanism;

Fig. 3 is a detail view of typical nozzle adjustment structure; and

Fig. 4 is a section of the nozzle showing the sealing means.

Referring to the schematic flow diagram of Fig. 1, the wind tunnel unitincludes the air compressor 8, the high pressure reservoir 9, the valve10, nozzle 12, evacuated tank 13 and vacuum pumps 14. A settling chambermay be placed between the valve and nozzle 12 to reduce These units areall connected in series, as named, so that pronounced air flow may bedeveloped through the nozzle, in the direction as indicated by thearrow.

The nozzle is divided into three sections, the effuser 15 to produce airacceleration with gain of kinetic energy and loss of pressure energy,the test section 16 for insertion of models and test of theiraerodynamic characteristics. and the diffuser 17 for converting thekinetic energy of air flow back into pressure for discharge into thetank 13 or atmosphere. Throat restrictions 18 and 19 are thus formedrespectively at the effuser and diffuser.

In order to secure variation in the effuser-diffuser dimensions andoutline and thus control speed condition in the test section, the nozzleis constructed of four main parts, including stationary parallel wallsections 20, 21 (Fig. 4) and movable nozzle sections 22 and 23positioned between the wall sections. As illustrated in Fig. 4 thisarrangement produces a rectangular cross section so that on movement ofthe movable nozzle sections a linear variation in cross sectional arearesults, lending itself to.

easy control of air flow. Each nozzle section 22, 23

one form; of nozzlesection: adjusting mechanism.

2,696,110 Patented, Dec. 7, 1.954

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iszshaped allochirally on facing areas to obtain the etfuserdifiusercontour desired for formation of the test nozzle. Section 16., as shownin Fig. 2', has movable support means, diagrammatically indicated bystrap attachments 25, 26-, 27', andi28, employed to shift these nozzlesectionsbctween thelimits illustrated, for example, by the fuli'ancibroken outlines 311 and 31 of the nozzle face; and, to this end, eachstrap attachment is connected to themovable sections- 22 and23 by pivotpins 29. It is particularly pointed out that constriction 18 has mini?mum crosssectional area at the extreme down stream end thereofwith theup stream contour of the constriction diverging. Since the adjacentpivot is upstream from this smallest area, as shown in Fig, 2, anyoutward movement of power-element 26 will enlarge thearea of both thedown. stream. and up stream constrictions and, thus, both: constrictionsmaybe modified in the same sense by asingle power element adjacent thedown stream end of the nozzle.

Since the supports 2528 may be adjusted separately or simultaneously bymanualor motor means; it is evident. that a widerange of settings may bemade for the movable nozzle sections, thus securing high flexibilityinair' speed: control.

Fig. 31 illustrates a practical structural arrangement of Intermediatethe side plates 20 and 21 andadjacent the top edges: thereof is securedfi xedl'y a cross block 40 centrally apertured to receive a shaft 41.The shaft is grooved near: one end, as at- 42, and aball bearing raceway including rings 43 andand bearings 45 secured" to the grooved? shaftsection and the inner face. of the block aperture. top of the blockaperture to hold bearing ring 44 in place.

At the upper end of the shaft above the block 40 a drive wheel 47 ismounted; and to side plate 20 a re versible motor unit 48 having a powershaft 49 terminating in a pulley 50 is secured, pulley belt 51 providingpower drive connection between the pulley wheels 50 and 47. Usualcontrol means (not shown) are provided to connect and control the supplyof power to the motor 48; or, alternatively, manual means may be used inplace of the motor unit.

The shaft 41, as supported for rotation on block 40, is formed with anexternal screw thread 55 at its inner or lower end, as shown in Fig. 3.Adapted for threaded engagement of this shaft end 55 is a block 56having pivot pins 57 fixed thereto on two opposite sides, as by lockpins 58, and extending into pin bearing apertures 59 formed in sidesupport 60 and 61. These side blocks, in turn, are fixed to the sidewalls 62 and 63 of the U- shaped upper movable nozzle section 22, sothat the center block 58 which receives the screw shaft 41 has pivotedmovement with reference to the nozzle section 22. Since this adjustmentmechanism is placed at both ends of the nozzle section. it is apparentthat either end may be adjusted independently of the other and hencesuccessive or simultaneous adjustment may be made.

The apparatus of Fig. 3 is exemplary of independent control at one endonly of a movable nozzle section. However, the motor connections may bearranged to actuate simultaneously a similar control unit at theadjacent end of the other nozzle section. This may readily be done byroviding an extension of the motor shaft to 'the under edge of sideplate 20 for connection to the opposite pulley system.

In order to prevent air leakage between the side plates 20 and 21 andthe sides 62, 63 of a nozzle section there is embedded in a lengthwisegroove on either side of the section adjacent the outer edges thereofsquare rubber tubes which frictionally engage the inner surfaces of sideplates 20 and 21.

In operation, the starting nozzle blocks 22, 23 are positioned as shownin Fig. 2 in broken lines with the area of the second throat 19sufliciently large to pass the transient shock system which precedes thesupersonic flow as it is established progressively further downstream inthe nozzle. The valve 10 is then opened and the effuser expands the highpressure air to supersonic speeds in the test section where it remainsapproximately constant. Beyond the test section the air is recompressedin the An annular strip 46 is insertedat the diffuser to a lowersupersonic speed and downstream of throat 19 there is a slight expansionfollowed by a normal shock system and subsequent difiusion from subsonicvelocities to a state of rest.

The air supersonic speed thus attained in the nozzle is relatively lowdue to the displaced sections at throat 18. The nozzle is now adjustedto a more constricted throat area as shown in full lines in Fig. 2, thusproducing a high supersonic speed value. By starting in this way at alow supersonic speed and hence a low starting compression ratio, andthen increasing the speed to high supersonic values, there is obtained aconsiderable saving in power, and this factor with the simplicity ofstructure and flexibility of use combine to make this nozzle ofconsiderable importance in wind-tunnel equipment.

While specific mechanism and arrangements have been described to setforth the substance of the invention, it is apparent that modificationsmay be made subject to limitations imposed by the claims as heretoappended.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. A wind tunnel nozzle comprising an elongated tube having at least twosuccessive constrictions therein spaced by an enlarged recess, a movablesection in said nozzle including joined peripheral segments of saidconstrictions and recess, support elements adjacent each constrictionfor supporting each end of said movable section, said support elementseach having a pivot connection to said section, the up streamconstriction having the point of smallest cross-sectional area downstream from the transverse plane including the pivot connection, and asingle power mechanism connected to the down stream section pivot forchanging the cross-sectional area of both of said constrictions.

\ eluding said pivot connection,

2. A wind tunnel nozzle comprising an elongated tube having at least twosuccessive constrictions therein spaced by an enlarged recess, a movablesection in said nozzle including joined peripheral segments of saidconstrictions and recess, a support element adjacent the upstreamconstriction having a pivot connection to said section, the upstreamconstriction having the point of smallest crosssectional area downstreamfrom the transverse plane inand a single power device for moving saidsection on said pivot connection, said power device being connected tosaid section at a point displaced from said pivot connection.

3. The wind tunnel nozzle as defined in claim 2,

with said power device attached to said movable section adjacent thedown stream end thereof, the power movement of the device at the pointof attachment to said section being transverse to the nozzle axis.

4. The wind tunnel nozzle as defined in claim 2,

. said upstream constriction smoothly diverging upstream at a uniformrate from the point of minimum cross-sectional area.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Hypersonic Research Facilities at the Ames Aeronautical Lab.,Journal of Applied Physics, vol. 21, 11,

'Nov. 1950, pp. 1150-1155.

